Background: Current understanding of the impact that sedative agents have on neurovascular coupling, cerebral blood flow (CBF) and cerebrovascular response remains uncertain. One confounding factor regarding the impact of sedative agents is the depth of sedation, which is often determined at the bedside using clinical examination scoring systems. Such systems do not objectively account for sedation depth at the neurovascular level. As the depth of sedation can impact CBF and cerebral metabolism, the need for objective assessments of sedation depth is key. This is particularly the case in traumatic brain injury (TBI), where emerging literature suggests that cerebrovascular dysfunction dominates the burden of physiological dysfunction. Processed electroencephalogram (EEG) entropy measures are one possible solution to objectively quantify depth of sedation. Such measures are widely employed within anesthesia and are easy to employ at the bedside. However, the association between such EEG measures and cerebrovascular response remains unclear. Thus, to improve our understanding of the relationship between objectively measured depth of sedation and cerebrovascular response, we performed a scoping review of the literature. Methods: A systematically conduced scoping review of the existing literature on objectively measured sedation depth and CBF/cerebrovascular response was performed, search multiple databases from inception to November 2020. All available literature was reviewed to assess the association between objective sedation depth [as measured through processed electroencephalogram (EEG)] and CBF/cerebral autoregulation. Results: A total of 13 articles, 12 on adult humans and 1 on animal models, were identified. Initiation of sedation was found to decrease processed EEG entropy and CBF/cerebrovascular response measures. However, after this initial drop in values there is a wide range of responses in CBF seen. There were limited statistically reproduceable associations between processed EEG and CBF/cerebrovascular response. The literature body remains heterogeneous in both pathological states studied and sedative agent utilized, limiting the strength of conclusions that can be made. Conclusions: Conclusions about sedation depth, neurovascular coupling, CBF, and cerebrovascular response are limited. Much further work is required to outline the impact of sedation on neurovascular coupling.

中文翻译：

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基于处理过的脑电图客观测量的镇静深度与脑血管反应之间的关联：人类和动物文献的系统范围概述。

背景：目前对镇静剂对神经血管耦合、脑血流量 (CBF) 和脑血管反应的影响的理解仍不确定。关于镇静剂影响的一个混杂因素是镇静深度，这通常在床边使用临床检查评分系统确定。这样的系统不能客观地解释神经血管水平的镇静深度。由于镇静深度会影响 CBF 和脑代谢，因此需要对镇静深度进行客观评估。在外伤性脑损伤 (TBI) 中尤其如此，新兴文献表明脑血管功能障碍在生理功能障碍的负担中占主导地位。处理后的脑电图 (EEG) 熵测量是客观量化镇静深度的一种可能的解决方案。这些措施在麻醉中广泛使用，并且很容易在床边使用。然而，这些脑电图测量与脑血管反应之间的关联仍不清楚。因此，为了提高我们对客观测量的镇静深度与脑血管反应之间关系的理解，我们对文献进行了范围审查。方法：对现有关于客观测量镇静深度和 CBF/脑血管反应的文献进行了系统的范围界定，搜索了从成立到 2020 年 11 月的多个数据库。审查了所有可用文献以评估客观镇静深度 [通过处理后的脑电图 (EEG) 测量] 和 CBF/大脑自动调节之间的关联。结果：共鉴定出 13 篇文章，其中 12 篇关于成人，1 篇关于动物模型。发现开始镇静会降低处理后的 EEG 熵和 CBF/脑血管反应测量值。然而，在初始值下降之后，在 CBF 中看到了广泛的响应。处理后的 EEG 和 CBF/脑血管反应之间存在有限的统计学上可重现的关联。在研究的病理状态和使用的镇静剂方面，文献主体仍然是异质的，限制了可以得出的结论的强度。结论：关于镇静深度、神经血管耦合、CBF、和脑血管反应是有限的。需要做更多的工作来概述镇静对神经血管耦合的影响。